1) Field of the Invention
The present invention relates to a torque transducer and a torque measuring device, and more particularly to a torque transducer for detecting a torque transmitted (loaded) to a torque transmission shaft based on a phase difference between pairs of rotating members and stationary members mounted on the drive side and load side of the torque transmission shaft, respectively, and a torque measuring device for measuring a torque transmitted to the torque transmission shaft, in accordance with an output of the above torque transducer.
2) Description of the Prior Art
It is well known to provide a torque measuring device for measuring a torque between a load side and a drive side of a torque transmission shaft connected to a prime mover such as a motor or engine, by detecting a torsion (shear strain) at a torque transmission shaft or torque detector shaft connected between the load side and the drive side of the torque transmission shaft.
The conventional torque measuring device, however, has a drawback in that the object to be measured is rotated, and the measured data is transmitted to a stationary device by a telemeter or slip ring, and therefore, the detection accuracy is low due to noise caused by the rotational contact of the slip ring or noise introduced from other sources.
To overcome the above drawback, there has been proposed a device for measuring the above torque by a non-contact process in which a relative phase difference between both rotating disks secured on the load side and drive side of the torque transmission shaft, respectively, is detected. For example, as shown in FIG. 10 illustrating the drive side of a torque detector shaft, a rotating disk 73 is coaxially fixed to a flange 72 mounted on the drive side 71a of the torque detector shaft 71, and a stationary disk 74 is fixedly and coaxially arranged in a position adjacent to the rotating disk 73. A plurality of elongated slits 74a, 73a are provided radially at equidistant intervals in the outer circumferential parts of the stationary disk 74 and the rotating disk 73, and a light receiver 75 is arranged in such a manner that it receives a light transmitted through the two slits 73a and 74a from a light projector 76. The same assembly as above is provided on the load side, i.e., at the left side of the torque detector shaft 71 (not shown), and the slits 73 a in the rotating disks 73 on both the load side and the drive side 71a are aligned with each other and the slits 74a of the stationary disks 74 on both the load side and the drive side 71a are also aligned with each other, (any misalignment between these slits must be allowed for by incorporating the amount of deviation in the result of the measurements). Upon rotation of the torque detector shaft 71, the rotating disk 73 is also rotated, and due to the alignment of the slits 73a and 74a, the light from the light projector 76 is transmitted through the slits 73a and 74a and received by the light receiver 75. During the rotation of the disk 73, the opening formed between the slit 73a and 74a is first opened by a small amount, is then fully opened, again becomes a small opening, and finally, is fully closed. Accordingly, as the rotating disk 73 is rotated, the amount of light received by the light receiver 75 repeats a cycle of (zero).fwdarw.(small).fwdarw.(large).fwdarw.(maximum).fwdarw.(large).fwdar w.(small).fwdarw.(zero). When the widths of the slits 73a and 74a in the circumferential direction are suitably set, the above cycle produces a sine curve, and therefore, the light receiver 75 outputs a signal having approximately a sine curve. Therefore, the degree of torsion at the torque detector shaft 71 can be detected by comparing the phase of the sine curve signal obtained at the drive side 71a with the phase of the signal obtained at the load side. Namely, if the torsion is zero, the relative difference in the phase of the above signals is also zero.
Nevertheless, upon starting and stopping, the rotation of the torque detector shaft 71, since only the drive side 71a is driven and the load side is not rotated, the rotating disk 73 of the drive side 71 and the rotating disk of the load side are not both rotated, and therefore, the above sine curve signal can not be obtained, i.e., the torque can not be measured. To overcome the above drawback, a countermeasure has been considered whereby, when the speed of rotation of the torque detector shaft 71 becomes less than a predetermined value, the stationary disk 74 is rotated by a predetermined amount by a drive force other than that of the drive side 71a. This, however, leads to other problems in that the constitution of the device and the necessary adjustments become complex.